The dragons loved the Playbrush and four offered the full £100,000 proposed. However, the founders decided they couldn't part with more than one per cent equity, and walked away. This reflected their confidence in a product that has already achieved 150,000 sales and transformed the tooth brushing habits of children worldwide.

Continuing their success

Since filming the show, Playbrush have received funding from Austrian financiers Speedinvest, Hansi Hansmann and former racing-car driver Harold Primat. Playbrush products are now available online at Tesco Direct as well as stores across Europe.

Paul Varga, co-founder of Playbrush, said: “Although inside the Den it may have been ambitious, outside of the Den our valuation has now led to successful seven-digit funding rounds from European investors and our smart toothbrush continues to go from strength to strength - allowing us to expand into new markets and make brushing fun for more kids.”

Jerry Allen, Director for Entrepreneurship, UCL Innovation & Enterprise, said: “I'm delighted Playbrush is going from strength to strength. It's a great example of how UCL’s Innovation & Enterprise department can help transform an idea into something bigger and real.”